Which of the following is considered the least reliable type of speed enforcement?

Pacing is considered the least reliable type of speed enforcement because it relies on the officer's perception and ability to maintain a consistent speed alongside the target vehicle. This method can be influenced by various factors, such as the officer's speedometer calibration, distractions while driving, and the potential for errors in judgment regarding the target vehicle's speed. Unlike more advanced technologies like radar or laser, which provide direct measurements of speed with minimal room for error, pacing inherently involves subjective elements and assumptions, making it less precise as a speed enforcement technique.

In contrast, radar and laser systems utilize technology that delivers accurate speed readings, while aircraft speed enforcement can cover larger areas and track multiple vehicles simultaneously from above. These methods offer more reliability in enforcing speed limits due to their technological basis, reducing the likelihood of human error. Thus, pacing's reliance on an officer's estimation and the variability in execution contribute to its classification as the least reliable option among speed enforcement techniques.